Disc drives are data storage devices that store digital data in magnetic form on a storage medium on a rotating information storage disc. Modern disc drives include one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (“heads”) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g., a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the information storage discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the information storage discs, so that when the actuator arms are pivoted, the heads move in an arc across the surfaces of the information storage discs.
Modern disc drives include one or more information storage discs mounted on the spindle motor. Spacers are typically mounted on the spindle motor between information storage discs to provide adequate separation between the discs for the actuator arms to movably locate the heads in relation with the disc surfaces. The information storage discs and disc spacers are collectively referred to as a disc pack. Typically, the disc pack is secured to the spindle motor hub by a downward clamping force of a disc clamp.
Disc clamps are usually stamped or milled. While milled clamps are more rigid and less prone to deflecting the abutting information storage disc surface, they are relatively expensive to produce. Consequently, the substantially less expensive leaf spring disc clamp, stamped from sheet metal, has become popular, and relatively prominent type of clamp used within the disc drive industry.
The stamped leaf spring disc clamp is typically shaped as a circular disc having a central portion and a rib portion. The central portion of the clamp has a washer-like shape and can be inclined relative to the rib portion. The central portion defines a centrally located aperture for receiving the disc clamp on the spindle hub. The rib portion of the disc clamp is peripherally located for contacting the inner diameter of the top information storage disc. A plurality of screw holes are symmetrically spaced in the central portion about the central aperture of the clamp for receiving screws used to secure the disc clamp to the spindle hub, the torqued screws exerting a downward axial force through the disc clamp and onto the top information storage disc.
A critical functional aspect of the disc clamp, stamped or milled, is how centered the disc clamp is on the disc pack assembly. Un-even or non-centered disc clamps contribute to disc pack imbalances which often result in rotational vibrations within the disc pack assembly. Rotational vibrations cause undesirable variations in the read/write signals detected by the read/write heads, and cause unwanted noise from the disc drive. Additionally, non-centered disc clamps are more prone to offsets during mechanical shock events to the disc drive.
Accordingly, there is a need in the disc drive art for an inexpensive, stamped disc clamp having a centering feature that allows the disc clamp to be centered on the disc pack during installation and use. Against this backdrop the present invention has been developed.